You are able to view shared inboxes in the Webmail client in addition to just your personal email. Here's how to do it:
You can now access the inbox and features of the shared email account as you would with your own email account.
For more information about shared mailboxes, view the official Microsoft documentation here: https://support.microsoft.com/en-us/office/open-and-use-a-shared-mailbox-in-outlook-on-the-web-98b5a90d-4e38-415d-a030-f09a4cd28207